1. Field
Example embodiments relate to moving picture compression. Also, example embodiments relate to image search methods capable of performing motion estimation used for moving picture compression at high speed.
2. Description of Related Art
Advances in techniques associated with digital signal processing, storage mediums, and methods of transfer have resulted in development into multimedia services from services that were typically limited to voice information. Many approaches for compression have been developed to store and transfer massive quantities of data. In particular, in the latter half of the 1980's, technological enhancement was accelerated according to needs for coding and storage technique standards of digital moving picture information. The International Telecommunication Union (ITU) established H.261 and H.263 as the standards for moving picture services for wire and wireless telecommunication network systems, and the International Organization for Standardization (ISO) made MPEG-1, MPEG-2, and MPEG-4 the moving picture standards. As wireless communications continue to rapidly spread out, moving picture compression technique standards are needed that provide improved compression efficiency compared with related art compression methods and that accommodate various telecommunications systems. In recent years, H.264, established by the ITU and ISO, brought about improvement compared with related art standards such as MPEG-2, MPEG-4 (Part 2), and the like in the aspects of flexibility, ease of compatibility with various networks, and coding efficiency with moving pictures.
H.264 was developed for the purpose of providing improved image quality relative to related art video compression standards. The basic concept of H.264 is similar to that of H.263 and MPEG-4, but the details of implementation of H.264 are significantly different. For example, in the case of motion estimation/compensation, H.263 provides blocks whose sizes are equal to each other, while H.264 provides blocks whose shapes and sizes may be different from each other. Since H.264 supports a quarter pixel, it is possible to effectively reduce the amount of surplus data that is produced via motion estimation as compared with related art standards. As a result, H.264 has 2.3 times higher compression efficiency than that of MPEG-2 and 1.5 to 2 times higher compression efficiency than that of MPEG-4. However, due to applying various block modes with respect to a plurality of reference images and conducting motion estimation, H.264 has drawbacks including quantity and complexity of computations. For example, the complexity of calculations in H.264 is approximately sixteen times higher than in MPEG-4 SP (Simple Profile).
When encoding using H.264, a motion estimation (ME) portion requires a large quantity of computations and takes up a lot of time. For example, in the case of using five reference images for motion estimation, the motion estimation takes about 80% of the total encoding time. Therefore, there is a need for a technique to effectively reduce the quantity of motion estimation computations in order to use H.264 compression technique for real-time applications.